5-Chloro-2-hydroxybenzenesulfonic Acid is obtained from 2,5-dichlorobenzenesulfonic acid by partial hydrolysis with sodium hydroxide solution in water at 170 – 190 ℃ and precipitation with concentrated hydrochloric acid. Used to prepare 5- chloro-2-hydroxy-3-nitrobenzenesulfonic acid, whichisthen reducedto 3-amino-5-chloro-2-hydroxybenzenesulfonic acid.
